The present invention relates to the art of joining the individual pieces of sheet material capable of being bonded along their abutting edges, parallel to the grain to form a continuous web which may then be cut into desirable lengths for further use. The most common application of this type of apparatus is in the production of composite veneer sheets which are used in the manufacture of polywood panels. The composite veneer sheet is made up of random width veneer pieces which are edge glued to form a continuous ribbon of veneer which is then clipped in suitable lengths to form 4 .times. 8 panels for instance.
As commonly practiced, this process includes the steps of jointing or edge trimming at least one edge of the veneer pieces, applying a coating of adhesive such as contact cement on the edges and then placing the veneer pieces in edge-abutting relationship while pressuring or crowding the pieces against one another as they are moved along a line of travel. A conventional guillotine clipper is usually located at the outfeed end of the crowder and serves to cut the continuous ribbon into usable size sheets. The individual veneer pieces are not perfectly rectangular but are more often trapezoidal as is the resulting composite sheet.
With conventional equipment, the individual pieces enter the crowder line which has at least two sections comprising the infeed and the outfeed sections. The infeed crowder section has upper and lower chains, or the equivalent, contacting the surfaces of the veneer pieces and are held under considerable pressure while being continuously driven. In order to provide the crowding action, the outfeed crowder chains are provided with a lower pressure acting on the upper and lower faces of the pieces and have no positive drive. This arrangement causes the incoming veneer pieces to be moved against the preceding pieces as they are pushed through the outfeed section.
The conventional edge gluing process as described results in significant veneer waste which the present invention is successful in alleviating. Since, as explained, the individual veneer pieces are not exactly rectangular and are more often trapezoidal, the incoming veneer piece which is positively gripped by the infeed crowder chains is forcefully moved forward and is not allowed to move at all in a lateral direction. Since the outfeed chain section places very slight pressure on the faces of the moving veneer ribbon, the effect is that the incoming veneer piece is held rigid while the ribbon is caused to move laterally one way or the other as the slanted edge of the incoming piece is mated against the end of the ribbon. This movement can be visibly observed as the ribbon continues to move and may be in the neighborhood of a couple of inches, first to one side and then to the other. The result is that the clipper does not clip off a rectangular 4 .times. 8 veneer sheet as intended but, instead, because of the "snaking" of the ribbon, cuts a more or less trapezoidal composite sheet. The result is that a wedge of from 21/2 to 31/2 inches of veneer is usely wasted on each sheet because it is not square. Over a years period, this waste in a typical plywood mill may represent several hundred thousand dollars loss because of the present high price of veneer. In the event that trimming saws are used, the weaving or snaking of the ribbon as it issues from the crowder mill also cause severe binding. The result of such binding may be that of splitting or crumpling the thin veneer sheet.